Mars awash with evidence of water

NASA has announced further evidence of a watery history on Mars, from both its rovers.

On one side of the planet, a flat rock, dubbed Escher because of its patterned surface, shows signs that the surrounding area has seen water come and go more than once. On the other side, attempts to find a rock unaltered by water have been in vain.

Early on in the mission, the rover Opportunity established that its immediate area had been submerged, long ago, before drying out into a wide plain. The new findings suggest that, after an impact created a stadium sized crater, some rocks got wet for a second time.

The Escher rocks' surfaces are crossed by a cracks that break their faces into a network of polygons which closely resemble dried-out mud-flats on Earth. There are other possible explanations for the shapes on the Escher rock, including a crater impact that caused the rock to fracture.

"When we saw these polygonal crack patterns, right away we thought of a secondary water event significantly later than the episode that created the rocks," said Dr. John Grotzinger, rover-team geologist from MIT.

Half way around the world, Spirit's team is nearly drowning in evidence of water. It first discovered that the bedrock had been significantly changed by water, then went looking for a rock that had not been eroded so they could get an idea of the environmental changes in the region. They couldn't find one.

Dr. Steve Squyres of Cornell University, principal investigator for the science payload on both rovers said: "All the rocks in the hills have been altered significantly by water. We're having a wonderful time trying to work out exactly what happened here." ®